These studies are designed to evaluate the clinical benefits achieved by iron chelation in patients with chronic iron overload. Desferoxamine is administered by subcutaneous infusion and iron removal is determined by measurement of the serum ferritin and periodic non-invasive measurement of liver-iron concentration. Clinical status is evaluated by standard parameters including non-invasive testing of cardiac and endocrine function as indicated by the patient's age and risk category. The study is designed to document the natural history of severe beta thalassemia, treated effectively with regular transfusions and chelation therapy tailored to the patient's clinical status. The patients studied are both male and female, range in age from 5 to 70 years, and are Caucasian, African American, Oriental or Hispanic. A study of 59 patients with homozygous beta thalassemia followed for periods ranging from 5-10 years has been completed. Patients who are highly compliant with desferoxamine have remained free of evidence of cardiac and endocrine disease, whereas the control population of poorly compliant patients has exhibited greater than 50% mortality. Similar studies in adult patients with acquired bone marrow disorders requiring regular transfusions have also suggested a clinical benefit of Desferal treatment. We have added another year to the long-term follow-up of patients with congenital and acquired anemia requiring regular blood transfusions.